The World Anti-Doping Agency (WADA) has appealed to the Court of Arbitration for Sport (CAS) against an independent tribunal's decision in August to clear world No.1 Jannik Sinner of wrongdoing after he failed drug tests, WADA said on Saturday.

The tribunal's finding of "no fault or negligence" was not correct under the applicable rules, WADA said in a statement.

WADA said it would seek "a period of ineligibility of between one and two years" for Italy's Sinner, who won the Australian Open and the U.S Open this year.

The announcement was made while Sinner was on court against Roman Safiullin at the China Open in Beijing.

Sinner tested positive twice for an anabolic steroid in March but was not banned in a decision by an independent tribunal announced by the International Tennis Integrity Agency (ITIA) on Aug. 20 because the ITIA determined he was not to blame.

Sinner's accepted explanation was that the banned performance-enhancer entered his system unintentionally through a massage from his physiotherapist, who used a spray containing the steroid to treat their own cut finger.

WADA said it filed an appeal on Thursday to the Switzerland-based CAS.

"It is WADA's view that the finding of 'no fault or negligence' was not correct under the applicable rules," WADA said in a statement. "WADA is seeking a period of ineligibility of between one and two years. WADA is not seeking a disqualification of any results, save that which has already been imposed by the tribunal of first instance."

WADA suggested the rules were not followed correctly despite a prosecutor for tennis's integrity body -- which accepted Sinner's version of events -- being a lawyer who regularly works on high-profile cases for the global watchdog, including the successful appeal against Russian figure skater Kamila Valieva.

An appeal verdict at CAS could come quickly -- even within just a few months -- if the parties agree to cooperate. That's how it worked in another high-profile doping case in tennis involving Maria Sharapova.

Still, the case likely won't be resolved before Sinner begins the defense of his Australian Open title in January.

Sharapova tested positive at the Australian Open in January 2016 for the newly-banned heart medication meldonium. She was banned for two years in June that year by the International Tennis Federation.

The Russian star appealed to CAS, had an appeal hearing in New York before three judges that September, and four weeks later got the verdict that cut her ban to 15 months.

The entire process for Sharapova with CAS took just four months -- far shorter than most doping cases, which typically last for about one year. The timeline can stall with the complexities of picking a judging panel, finding a hearing date and parties exchanging documents and evidence from expert witnesses.

During the Indian Wells hard-court event in March, Sinner tested positive for low levels of a metabolite of Clostebol, a banned anabolic steroid that can be used for ophthalmological and dermatological use. It's the same drug for which San Diego Padres star Fernando Tatis Jr. was suspended by MLB in 2022.

Sinner tested positive again eight days later in an out-of-competition sample.

He was provisionally suspended twice by the tennis integrity body because of those test results, but he successfully appealed twice to an independent tribunal judge and was allowed to keep competing on tour.

Sinner said his test results happened because his fitness trainer purchased an over-the-counter spray called Trofodermin in Italy that contained Clostebol and gave it to Sinner's physiotherapist to treat a cut on the physiotherapist's finger. The physiotherapist then treated Sinner without wearing gloves.

The ITIA said it accepted Sinner's explanation, after 10 interviews with the player and his entourage, and the independent panel agreed at a hearing on Aug. 15.

Sinner later announced that he had fired his two trainers.

Information from Reuters and Associated Press contributed to this report.